MEXICO CITY, MEXICO—Using the remote-controlled Tlaloc II-TC robot, researchers from the National Institute of Anthropology and History have discovered three chambers at the end of a 2,000-year-old tunnel at Teotihuacán’s Quetzalcoatl Temple. The chambers, now full of mud and rubble, may have been used for royal burials and ceremonies. No depictions of the city’s rulers or their burials have ever been found, but archaeologists plan to clear out this last section of tunnel for further investigation.